High Linear Dynamic Range Research Articles

Reconfigurable perovskite X-ray detector for intelligent imaging

X-ray detection is widely used in various applications. However, to meet the demand for high image quality and high accuracy diagnosis, the raw data increases and imposes challenges for conventional X-ray detection hardware regarding data transmission and power consumption. To tackle these issues, we present a scheme of in-X-ray-detector computing based on CsPbBr3 single-crystal detector with convenient polarity reconfigurability, good linear dynamic range, and robust stability. The detector features a stable trap-free device structure and achieves a high linear dynamic range of 106 dB. As a result, the detector could achieve edge extraction imaging with a data compression ratio of ~50%, and could also be programmed and trained to perform pattern recognition tasks with a high accuracy of 100%. Our research shows that in-X-ray-detector computing can be used in flexible and complex scenarios, making it a promising platform for intelligent X-ray imaging.

High-responsivity self-powered deep-ultraviolet photodetector based on n-SnS2/p-GaN heterostructures

Deep-ultraviolet (DUV) photodetectors (PDs) have important applications in various fields, however, high manufacturing costs, complex fabrication processes, and high-power consumption limit their further development. Here, the combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods are used to grow in-situ vertical SnS2 (v-SnS2) thin film on a gallium nitride (GaN) substrate, thereby forming a v-SnS2/GaN p-n heterojunction (type-Ⅱ). With zero bias, the device exhibits excellent self-powered performance under 265 nm illumination. The sensor has a large responsivity of 3.525 A/W, a high specific detectivity of 1.767 × 1014 Jones, a high linear dynamic range of 97 dB, and a fast response speed (rise/decay time of 150.5/266.4 µs). This work demonstrates the great potential of SnS2/GaN heterojunction devices for deep-ultraviolet detection.

Self-powered and broadband CuSCN/Si heterojunction photodetector for multi-color imaging based on diffuse reflection mode

Copper thiocyanate (CuSCN) has been widely used in photodetectors (PDs). However, the reported CuSCN-based PDs are suffered from narrow operating wavelength range and relatively low photodetection performance. Here, we fabricate an CuSCN/Si heterojunction PD by a simple low-temperature solution spin-coating method achieving excellent performance. Our designed CuSCN/Si PD exhibits a broadband response range covering ultraviolet–visible-infrared, a high detectivity of 2.26 × 1012 Jones coming from an ultralow dark current of 23 pA, and a decent responsivity of 11 mA W−1, a high linear dynamic range of 122 dB, and short response time of 25/150 μ (rise and decay time). Moreover, we demonstrate multi-color imaging across the wide wavelength range, indicating the CuSCN/Si PD has a promising potential in the imaging field. This work may pave the way for fabricating low-cost, nontoxicity, and high-performance CuSCN-based PD and broadening its applications.

Self-adaptive fusion method for scientific CMOS image sensors with variable gain ratios and background values.

Image diagnosis is an important technique in transient process research of high-energy physics. High dynamic range scenes require high linear dynamic range imaging systems. Scientific CMOS (sCMOS) image sensors have widely been used in high-energy physics, nuclear medical imaging, and astronomical observation because of their advantages in the high linear dynamic range. In this paper, we study the gain ratio variation and background value variation of commercial sCMOS image sensors. A self-adaptive fusion method is proposed to realize the fusion of high linear dynamic range images. The proposed method only uses the high gain image and the low gain image of the sCMOS image sensor to evaluate the gain ratio and the background compensation. The measured results show that the error rates of the evaluated gain ratio and background compensation are less than 2% and 6%. Test results show that the self-adaptive fusion method realizes well the fusion effects, which efficiently avoids the influence of gain ratio variation and background value variation.

High‐Speed Graphene–Silicon–Graphene Waveguide PDs with High Photo‐to‐Dark‐Current Ratio and Large Linear Dynamic Range

Abstract2D materials (2DMs) meet the demand of broadband and low‐cost photodetection on silicon for many applications. Currently, it is still very challenging to realize excellent silicon‐2DM photodetectors (PDs). Here, graphene–silicon–graphene waveguide PDs operating at the wavelength bands of 1.55 and 2 µm, showing the potential for large‐scale integration, are demonstrated. For the fabricated PDs, the measured responsivities are ≈0.15 and ≈0.015 mA W−1 for the wavelengths of 1.55 and 1.96 µm, respectively. In particular, the PDs exhibit a high bandwidth of ≈30 GHz, an ultra‐low dark current of tens of pico‐amperes, a high normalized photo‐to‐dark‐current ratio of 1.63 × 106 W−1, as well as a high linear dynamic range of 3 µW to 1.86 mW (and beyond) at 1.55 µm. According to the measurement results for the wavelength bands of 1.55/2.0 µm and the theoretical modeling for the silicon–graphene heterostructure, it is revealed that internal photoemission and photo‐assisted thermionic field emission dominantly contribute to the photoresponse in the graphene–silicon Schottky junctions under moderately high bias voltage, which helps the future work to further improve the performance.

Vertical Architecture Solution-Processed Quantum Dot Photodetectors with Amorphous Selenium Hole Transport Layer

Colloidal quantum dots (CQDs) provide wide spectral tunability and high absorption coefficients owing to quantum confinement and large oscillator strengths, which along with solution processability, allow a facile, low-cost, and room-temperature deposition technique for the fabrication of photonic devices. However, many solution-processed CQD photodetector devices demonstrate low specific-detectivity and slow temporal response. To achieve improved photodetector characteristics, limiting carrier recombination and enhancing photogenerated carrier separation are crucial. In this study, we develop and present an alternate vertical-stack photodetector wherein we use a solution-processed quantum dot photoconversion layer coupled to an amorphous selenium (a-Se) wide-bandgap charge transport layer that is capable of exhibiting single-carrier hole impact ionization and is compatible with active-matrix readout circuitry. This a-Se chalcogenide transport layer enables the fabrication of high-performance and reliable solution-processed quantum dot photodetectors, with enhanced charge extraction capabilities, high specific detectivity (D* ∼ 0.5–5 × 1012 Jones), fast 3 dB electrical bandwidth (3 dB BW ∼ 22 MHz), low dark current density (JD ∼ 5–10 pA/cm2), low noise current (in ∼ 20–25 fW/Hz1/2), and high linear dynamic range (LDR ∼ 130–150 dB) across the measured visible electromagnetic spectrum (∼405–656 nm).

Self-Powered Solar-Blind UV Detectors Based on O-Terminated Vertical Diamond Schottky Diode with Low Dark Current, High Detectivity, and High Signal-to-Noise Ratio

Self-powered solar-blind UV detectors were fabricated using high-quality Ru/diamond Schottky diodes. Photocurrents of 1 nA and 1.3 nA were obtained for detector Semi and Mesh under the condition of zero bias and 220 nm UV light irradiation, while the dark currents of these two detectors were 0.53 pA and 0.007 pA at 0 V, respectively. Photosensitive areas of detector Semi and Mesh were 1 mm2 and 0.74 mm2, respectively. Rectification ratios as high as 1.5 × 107 and 5.7 × 108 at ±5 V for Semi and Mesh were obtained, showing good rectifying characteristics for the vertical Schottky diodes. Responsivities at 0 V of Semi and Mesh were 10.3 mA/W and 16.2 mA/W, respectively. High detectivities of 3.8 × 1012 Jones and 5.2 × 1013 Jones for detector Semi and Mesh indicate excellent self-powered detection performance. To make a comprehensive comparison of the performance of diamond solar-blind UV detectors, a log(Iph) versus log(Idark) graph was proposed, and the detector in this work showed an ultrahigh SNR of 2 × 105. A high linear dynamic range of 105.9 dB was achieved for the self-powered detector Mesh.

Impact of Ligands on the Performance of PbS Quantum Dot Visible–Near‐Infrared Photodetectors

AbstractSolution‐processed lead sulfide quantum dots (PbS QDs) are an excellent candidate for photodetector applications because they exhibit broadband absorption, a wide range of tuneable bandgaps, high stability in air, and mechanical flexibility. However, a crucial criterion for the fabrication of high‐performance photodetectors is the selection of the ligands, which can facilitate charge carrier transport between the PbS QDs and passivate the surface defects. In this work, the authors have studied the effect of traps on the performance of PbS QD photodetectors that are fabricated using different types of ligands, using intensity‐dependent photoresponse dynamics. The best devices with lead halide ligands show a dark current density of 5 × 10−9 A cm−2 at −0.2 V, which is one of the lowest values reported thus far for solution‐processed PbS QD‐based photodetectors. Moreover, these devices show a high linear dynamic range (≈90 dB) and high detectivity (>1013 Jones), in addition to an f‐3 dB of greater than 100 kHz without the application of an external voltage bias at a wavelength of 784 nm. These results suggest that with an appropriate selection of ligands, solution‐processed photodetectors with a lower density of traps and a better device performance can be fabricated.

Flexible short-wavelength infrared photodetector based on extrinsic Sb2Se3

One-dimensional antimony selenide (Sb2Se3), enjoying intriguing optoelectronic properties, has drawn extensive attention in solar cells and broadband photodetection. Limited by the bandgap, the reported Sb2Se3 photodetectors always focus on the detection of visible and near-infrared (<1050 nm). Extending the detection waveband can greatly enrich the applications of Sb2Se3 photodetectors. Extrinsic photoconduction is an attractive strategy for extending the detection waveband, for example, the extrinsic Si detector for short-wavelength or long-wavelength infrared detection. However, Sb2Se3 extrinsic photoconduction has not been reported yet. Herein, the extrinsic photoconduction, attributed to the intrinsic point defects, is observed in Sb2Se3 for the first time, which induced a broadened short-wavelength infrared detection of 1650 nm at room temperature. Furthermore, the Sb2Se3 photodetector is fabricated on a flexible polyimide substrate. Meanwhile, the Sb2Se3 photodetectors also demonstrate a fast response speed (rise of 9 µs and fall of 11 µs), a high linear dynamic range of 98 dB, and wide -3dB bandwidth of 163 kHz at 1300 nm. This extrinsic-photoconduction provides feasible design strategies to broaden the detection waveband of the Sb2Se3 photodetectors and can be extended to other chalcogenides.

Transparent graphene electrodes based hybrid perovskites photodetectors with broad spectral response from UV–visible to near-infrared

A new class of transparent graphene electrode based organic–inorganic halide perovskite photodetectors with broad spectral response is developed. These ultrasensitive devices exhibit high ON/OFF current ratio, high linear dynamic range, broad spectral range, excellent detection for weak light and easy fabrication with low-cost. Their semi-transparent feature and distinct photodetecting function for both sides would provide new applications affecting our daily lives.

Photodetector Based on CsPbBr3/Cs4PbBr6 Composite Nanocrystals with High Detectivity

High-quality, all-inorganic CsPbBr3/Cs4PbBr6 composite perovskite nanocrystals (NCs) were obtained with all-solution-processing at room temperature, and a photodetector (PD) with high detectivity was realized based on CsPbBr3/Cs4PbBr6 NCs. The detectivity (D*) of the proposed PD is 4.24 × 1012 Jones under 532 nm illumination, which is among the highest levels for PDs based on all-inorganic perovskite NCs. In addition, a high linear dynamic range (LDR) of 115 dB under 1 V bias was also realized. Furthermore, the underlying mechanism for the enhanced performance of the proposed PD was discussed. Our work might promote the preparation of high-performance PDs based on dual-phase all-inorganic perovskite nanocrystals.

High-Performance Two-Dimensional Perovskite Ca2Nb3O10 UV Photodetectors.

We first report two-dimensional (2D) perovskite Ca2Nb3O10 ultraviolet photodetectors (UV PDs), which are prepared via a facile calcination-exfoliation method. The 2D Ca2Nb3O10 PDs demonstrate high performance at 3 V at 280 nm, high responsivity (14.94 A W-1), high detectivity (8.7 × 1013 Jones), high spectral selectivity (R280/R400 = 8.84 × 103), fast speed (0.08/5.6 ms), and long-term stability, exceeding those of most reported UV PDs. Furthermore, the Ca2Nb3O10 PDs integrated with poly(ethylene terephthalate) (PET) show excellent flexibility and have high linear dynamic range (96 dB). Our work provides a general strategy for searching new UV PDs based on numerous layered niobates. The Ca2Nb3O10 nanosheets may be one of the optimum semiconductor materials for next-generation high-performance UV PDs.

Detecting Cysteine in Bioimaging with a Near-Infrared Probe Based on a Novel Fluorescence Quenching Mechanism.

Near-infrared (NIR) fluorescent probes are very significant for detecting cysteine in biological systems. Herein, we report a highly selective and sensitive NIR turn-on fluorescent probe (BDP-NIR) based on BODIPY with large Stokes shift (105 nm) for detecting Cys. We clarified the sensing mechanism based on the different thiol-induced SN Ar substitution/rearrangement reaction of the probe with cysteine and homocysteine/glutathione, which leads to the corresponding amino- and thiol-BODIPY dyes with distinct photophysical properties. Moreover, a novel mechanism of fluorescence quenching was demonstrated by density functional theory calculation. The reason for the fluorescence quenching of the probe might be intersystem crossing (from singlet to triplet excited state). Moreover, BDP-NIR had a high linear dynamic range of 0-500 μM, which was promising for detecting cysteine quantificationally. Significantly, BDP-NIR was capable of sensing endogenous cysteine in living cells and in vivo.

Perovskite Photosensors Integrated with Silver Resonant‐Cavity Color Filters Display Color Perception Beyond That of the Human Eye

AbstractOrganic hybrid perovskite‐based photosensors generally display high responsivities and ultrafast response speeds, but their high dark currents with low detectivities have impeded their commercial applications. In this study, these problems are overcome by modifying the device structure and performing defect passivation of the perovskite. An inverted ITO/NiOx/perovskite/PCBM/BCP/Ag structure is applied to minimize the leakage current from the interlayers. In addition, a urea additive is embedded and the thickness of the perovskite layer is optimized, resulting in an ultralow dark current (&lt;2 pA), a peak detectivity of greater than 1.42 × 1014 Jones, and a high linear dynamic range (LDR) of up to 162 dB (in the response range from 20.25 to 6.80 × 10‐8 mW cm‐2). Using high‐purity color filters, combined with a well‐defined white light illumination system derived from a 3A solar simulator, the photosensitivity is evaluated under light of various hues and intensities (down to 10‐9 mW cm‐2). The optimized color sensors under blue, green, orange, and red hues of light display LDRs of greater than 139 dB in the mesopic vision regime (wavelengths: 400–700 nm) between 10‐6 and 10‐3 mW cm‐2—outperforming human visual color perception.

CAOS line camera.

Proposed and demonstrated is the coded access optical sensor (CAOS) line camera, a one-dimensional or line version of the two-dimensional (2D) digital-micromirror-device (DMD)-based CAOS camera. The proposed line camera design includes a precise dual-axis mirror scanning galvo system incorporating feedback control that eliminates the need for mechanical motion of either the camera or the target. CAOS line scan imaging experiments using a white light source with two test targets are conducted and compared with non-scan 2D CAOS imaging. Specifically, a 2D DMD operated as both a full-frame and a line modulator is used to demonstrate both full-frame (${127} \times {45}$127×45 pixels) and line (127 pixels) scan CAOS imaging. Also demonstrated is an increase in field of view (FOV) of the camera unit using the galvo system with FOV increased by factors of 2.87 and 1.67 in the horizontal and vertical directions, respectively. In addition, proposed for future implementation is a CAOS line camera design that allows analog and hybrid analog-digital time-frequency CAOS-mode irradiance coding for realizing improved inter-pixel cross talk. The CAOS line camera versus a 2D image sensor camera is suited for broad-spectrum large area/FOV imaging applications where high linear dynamic range and low contrast recovery are critical challenges, such as in active illumination inspection of archeological and art works and industrial machine parts.

Self-powered diamond ultraviolet photodetector with a transparent Ag nanowire electrode

A novel diamond UV photodetector with a transparent Ag nanowire (NW) electrode was fabricated. A transparent Ag NW network was spin-coated on single crystalline diamond to form a Schottky contact, which had a barrier height of about 1.37 eV obtained by XPS measurements. Meanwhile, multilayered metals of Au/Pt/Ti were evaporated on the diamond sample to form ohmic contacts. Compared to a Au/Pt/Ti-Au/Pt/Ti diamond photodetector, the Au/Pt/Ti-Ag NW diamond photodetector exhibited relatively high responsivity under 220 nm (18 mA W−1), high linear dynamic range (41 dB), and short response time (0.12 s for rise time, 0.56 s for decay time). In particular, the Au/Pt/Ti-Ag NW diamond photodetector displayed high photocurrent of about 200 pA at zero-bias, indicating its potential for creating self-powered devices.

Self-powered CsPbBr3 nanowire photodetector with a vertical structure

Single crystal halide perovskite nanowires (NWs) have attracted much attention for use in high-performance photodetectors (PDs) due to their high photoluminescence quantum yields, large carrier mobilities, and long carrier diffusion lengths. So far, most high-performance NW PDs are fabricated based on individual or aligned NWs which require complicated preparation processing. Furthermore, it is challenging for these NW PDs to possess self-powered operation characteristics. Here, we report self-powered perovskite NW PDs with a vertical p-i-n structure in which the CsPbBr3 NWs are grown by a combination of solution-phase and halide exchange processes. Before depositing the hole selective layer, poly(methyl methacrylate) is coated on perovskite NW film to fill the internal voids, which passivates surfaces of perovskite NWs and reduces the dark current. Our optimized CsPbBr3 NW PDs show dark current density as low as 4.0 nA cm−2 and photocurrent density as high as 22.9 mA cm−2 under a 473 nm laser illumination with intensity of 641 mW cm−2, leading to a high linear dynamic range of 135 dB. In addition, our perovskite NW PDs display highly self-powered performance with ultrohigh on/off ratios of above 106, responsivity of up to 0.3 A W−1 and detectivity of up to 1 × 1013 Jones at 0 V.

High Performance BiOCl Nanosheets/TiO2 Nanotube Arrays Heterojunction UV Photodetector: The Influences of Self‐Induced Inner Electric Fields in the BiOCl Nanosheets

AbstractBiOCl nanosheets/TiO2 nanotube arrays heterojunction UV photodetector (PD) with high performance is fabricated by a facile anodization process and an impregnation method. The heterojunction at the interface and the internal electric fields in the BiOCl nanosheets faciliate the separation of photogenerated charge carriers and regulate the transportation of the electrons. Compared with the large dark current (≈10−5 A), low on/off ratio (8.5), and slow decay time (&gt;60 s) of the TiO2 PD, the optimized heterojunction PD (6‐BiOCl–TiO2) yields dramatically decreased dark current (≈1 nA), ultrahigh on/off ratio (up to 2.2 × 105), and fast decay speed (0.81 s) under 350 nm light illumination at −5 V. Moreover, it exhibits an increased responsivity of 41.94 A W−1, a remarkable detectivity (D*) of 1.41 × 1014 Jones, and a high linear dynamic range of 103.59 dB. The loading amount and growth orientations of the BiOCl nanosheets alter the roles of the self‐induced internal electric field in regulating the behaviors of the charge carriers, thus affecting the photoelectric properties of the heterojunction PDs. These results demonstrate that rational construction of novel heterojunctions hold great potentials for fabricating photodetectors with high performance.

Systematic Optical Design of Constituting Layers to Realize High‐Performance Red‐Selective Thin‐Film Organic Photodiodes

AbstractA high‐performance red‐selective thin‐film organic photodiode (OPD) is designed. Dual‐band absorbing poly[(2,5‐bis(2‐hexyldecyloxy)phenylene)‐alt‐(5,6‐difluoro‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]‐thiadiazole)] (PPDT2FBT) is introduced as the photoactive donor layer of a planar heterojunction OPD in conjunction with a sol–gel synthesized ZnO acceptor layer. The active layer thickness is systematically controlled to suppress band II absorption (λmax = 420 nm) of PPDT2FBT without sacrificing band I absorption (λmax = 650 nm). The optimal PPDT2FBT thickness is 320 nm to realize red‐selective absorption while maintaining the low dark current density of the OPD (predicted by optical simulation conducted using the transfer matrix method). In addition, the introduction of ZnO (with a strategically determined thickness) as an acceptor layer in front of PPDT2FBT in an illumination pathway enables further suppression of band II absorption because of the blue color filter effect. Consequently, the resulting OPD with a device architecture of indium tin oxide/ZnO/PPDT2FBT/MoO3/Ag shows an outstanding red‐selective photodiode performance with peak detectivity up to 3.04 × 1012 Jones and a high linear dynamic range of 116 dB.

Nanocrystalline Perovskite Hybrid Photodetectors with High Performance in Almost Every Figure of Merit

AbstractConversion of photon into electron is a phenomenon of great importance in nature. Photodetectors based on this principle have immense potential applications at the frontiers of both scientific and industrial communities, thus affecting the daily life. Herein, a novel class of high‐quality organic–inorganic trihalide perovskite nanoscale hybrid photodetectors is presented based on carbon electrode−molecule junctions working at mild conditions. Almost every figure of merit with high performance, such as highest responsivity, highest photogain, high detectivity, high linear dynamic range, and a broad spectral response, could be achieved simultaneously in a single device under different biases. These significant achievements benefit from rational choices of novel energy loss‐prevented hybrid perovskite nanocrystals as active materials and optimized carbon electrode−molecule junctions as device architectures, which leads to a hybridization mechanism of photodiodes and photoconductors. These investigations demonstrate a useful photodetector platform that might lead to many future photoelectric conversion applications in the practical way.